Electrochemical sensors are commonly used to detect or measure the concentrations of in vivo analytes, such as glucose. Typically in such analyte sensing systems, an analyte (or a species derived from it) is electro-active and generates a detectable signal at an electrode in the sensor. This signal is then correlated with the presence or concentration of the analyte within a biological sample. In some conventional sensors, an enzyme is provided that reacts with the analyte to be measured, the byproduct of the reaction being qualified or quantified at the electrode. In one conventional glucose sensor, immobilized glucose oxidase catalyzes the oxidation of glucose to form hydrogen peroxide, which is then quantified by amperometric measurements (e.g. change in electrical current) through one or more electrodes.
A variety of electrochemical glucose sensors are multi-layered, comprising electrodes on top of and/or coated by layers of various materials. Multilayered sensors have a number of desirable properties including the fact that the functional properties of such sensors can be tailored by altering certain design parameters (e.g. number of internal layers, layer thickness, electrodes area and architecture etc). The fabrication of such multilayered sensors can require complicated processes steps that, for example, ensure that the various material layers exhibit appropriate functional characteristics, are of a uniform consistency, and are adapted to adhere to the group of materials that make up a stable sensor stack. In this context, certain electroplating processes can result in plated electrodes having a non-uniform surface, for example one that exhibits excessive growth at electrode edges. This edge growth can then cause non-uniformity in the subsequent layers of materials that are coated onto such electrodes, a phenomena which appears to contribute to certain undesirable glucose sensor phenomena, including layer delamination, sensor signal variability and high oxygen responses.
There is a need for methods and materials that can provide multilayered amperometric sensors with a number of desirable characteristics such as stability and optimized oxygen responses as well as improved manufacturing processes for fabricating such sensors.